Modify stride assertion in `numpy-map.hpp` to be valid for empty vector (#321)

* Set stride assert to be less than INT_MAX

* Remove extra print calls and flush on print

* Revert "Remove extra print calls and flush on print"

This reverts commit cc7db3d0.

* core: fix assert

Co-authored-by: Justin Carpentier <justin.carpentier@inria.fr>